Observation of Changes in Partial Discharge Activity in Artificial Voids Based on Analysis of $\Phi-\mathrm{q}-\mathrm{n}$ Characteristics and Light Emission Distribution of Partial Discharge

To investigate the degree of partial discharge degradation of resins and resin composites due to long-term application of voltage, attempts have been made to determine changes in discharge activity based on
$\Phi-\mathrm{q}-\mathrm{n}$
characteristics. However, it was not possible to accurately determine the actual discharge activity occurring within the defects from the measurement of the discharge amount alone. Therefore, an attempt was made to analyze the changes in discharge activity by visualizing the discharge emission inside defects and correlating the actual discharge state with changes in the
$\Phi-\mathrm{q}-\mathrm{n}$
distribution. In this study, a spherical electrode/polyethylene terephthalate (PET)/cylindrical void/PET/flat plate electrode system was employed as the artificial defect structure, and an indium tin oxide (ITO) transparent electrode was used as the flat plate electrode to enable direct observation of the light emission during partial discharge generation. This enabled the analysis of changes in the
$\Phi-\mathrm{q}-\mathrm{n}$
distribution and discharge state for investigating the changes in discharge activity. In this study, the changes in the discharge activity during long-term voltage application in a sealed void structure were investigated. The results demonstrated that even under the same void structure and test voltage conditions, protrusions may be generated because of discharge byproducts, and that the discharge occurring in these protrusive structures significantly affected the discharge activity and erosion morphology.